This invention relates to electrodes, particularly for use in Electromyography (EMG) and Nerve Conduction Velocity (NCV) measurement, and more particularly to such electrodes that are disposable. The invention further relates to a kit containing such electrodes.
The invention presents a disposable disc electrode, a disposable ground electrode and a disposable digital ring electrode and a kit containing same.
EMG is the study of electrical activity of nerves and muscles. It is useful in diagnosis of diseases such as Carpal Tunnel, Amyotrophic Lateral Sclerosis (ALS), Polio and Myasthenia Gravis.
The examination has two portions which vary significantly in practice and procedure:
1. Needle EMG: This portion of the examination is a volitional recording made from within the muscle, utilizing a needle electrode--sometimes with a surface reference electrode--and requiring a grounding electrode for grounding the patient.
The frequency of response is typically 2 Hz to 10 Khz with amplitudes varying from 20 Uv to as much as 10 mV. Electrodes are moved several times within an examination procedure. Impedance the electrode/patient interface is typically 15-20 k ohm or more. It is not typically measured nor is any pre-application prepping done to the skin.
2. NCV: This portion of the examination is an evoked respons using an electrical stimulus applied superficially to a nerve. The electrodes used for stimulating and recording are often used interchangeably. The sensory NCV involves stimulating and recording from nerves. A typical stimulus of 0.1 ms --50-75 volts -25 Ma is given superficially.
The response occurs 1.5 to 4 ms after the stimulus. Characteristics are 20 Hz-2 Khz, with amplitude 10 Uv to 50 Uv, typically. One set of electrodes is usually placed around a digit --either fingers or toes. This electrode is typically designed as a wraparound. The other set of electrodes is placed on a flatter portion of the body--usually at the wrist, or on the foot--and is usually a set of 10 mm discs.
The Motor Nerve Conduction involves stimulating a nerve superficially and recording superficially from a muscle. The stimulus is typically 150 V 0.1 ms-duration 60 Ma, applied through handheld or taped on electrodes about 10 mm diameter with spacing of 1-2 inches between; 3 or 4 different stimulating sites are used for each muscle. The response follows the stimulus by 2-15 ms, having an amplitude of 1 mV-50 mV and bandpass of 2 Hz-10 kHz.
The EMG/NCV examination requires use of a variety of surface electrodes for recording and stimulation. Current technology utilizes reusable, stainless steel or dampened felt electrodes in varying shapes and sizes. The electrodes are fastened in place with adhesive tape or VELCRO hook and loop connected straps after either wetting or applying electrolyte.
Some technicians use mild abrasives to lower skin resistance prior to electrode application. During the test procedure gel, tape, etc., are used each time electrodes are moved, which is typically 12 times during an examination. After testing is completed, the electrodes must be washed and, ideally, disinfected. However, with the advent of disposable EMG needles already accepted in the laboratory, there is a growing preference for the remainder of the examination electrodes to be disposable.
The primary advantages of the electrodes according to the present invention are as follows:
a. No need for additional paste, tape.
b. Better recording using silver chloride.
c. Faster application.
d No electrode cleanup.
e. Faster patient cleanup.
f. Reduced risk of contamination.
g Cost recoverable and controlled.
h. Ability to be moved 4 or 5 times before adhesive failure.
Currently, make-do electrodes (disposable EmG or TENS) are being furnished for EMG/NCV use, but none cover the complete functional EMG/NCV requirements. This invention presents a kit containing the three different types of electrodes typically used in the EMG/NCV examinations. Disposability of the inventive electrodes means that physicians and technicians are enabled to enjoy the convenience of not cleaning electrodes and not having to deal with the patient preparation process. Accordingly, important objects of the invention are to provide disposable electrodes that attain the aforementioned advantages.
A patentability search on this disclosure found the following United States Patents:
______________________________________ U.S. Pat. No. Date Inventor(s) ______________________________________ 4,409,981 October 18, 1983 Lundberg 4,524,087 June 18, 1985 Engel 4,635,642 January 13, 1987 Cartwell et al. 4,640,289 February 3, 1987 Craighead 4,699,679 October 13, 1987 Cartwell et al. 4,732,111 January 26, 1988 Muttitt 4,742,828 May 10, 1988 Lundstrom 4,768,514 September 6, 1988 De Marzo 4,852,571 August 1, 1989 Gadsby et al. 4,890,622 January 2, 1990 Ferrari ______________________________________
Of the foregoing patents, it is believed that those to Lundberg, Engel and Gadsby et al., come closer than any of the others to being pertinent to the present invention.